Tibial resection instrumentation and surgical method

ABSTRACT

A method of preparing a patient&#39;s proximal tibia with a surgical saw and cutting instrumentation is disclosed. The method of the present invention prepares the patient&#39;s proximal tibial to receive a tibial implant. The patient&#39;s intramedullary canal is first reamed and then an intramedullary rod is placed in the intramedullary canal as a reference. A first cutting instrument is bound on the rod above the patient&#39;s proximal tibia. The first cutting instrument includes a stylus that is used to set the depth of cut by referencing the top of the proximal tibia. The proximal tibia is then transversely cut with the saw by tracking the first cutting guide surfaces with the saw. The first cutting instrument is removed together with its stylus. A secondary cutting instrument is then placed on the rod above the proximal tibia. The second cutting instrument has a cutter at its center for cutting longitudinally into the proximal tibia. A secondary cut is made on the proximal tibia by tracking the secondary cutting instrument and a guide surface provided on the upper end of the cutters that engage the center of the proximal tibia.

This is a continuation of copending application Ser. No. 08/388,983, filed Feb. 15, 1995.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to orthopedic surgical instruments and surgical methods and more particularly relates to an improved method and apparatus for resecting the patient's proximal tibia for installing a knee prosthesis. Even more particularly, the present invention relates to an improved method and apparatus for resecting a patient's proximal tibia using a preliminary cutting guide and then secondarily cutting the proximal tibia with a secondary cutting guide that has blades that penetrate the proximal tibia, the blades having upper guide surfaces thereon that guide a sawblade during cutting.

2. General Background

In knee joint replacement surgery, a surgeon typically affixes two prosthesis components to the patient's femur and tibia. These replacement components are typically known as the femoral component and the tibial component.

The femoral component is placed on a patient's distal femur after the surgeon makes a plurality of surgical cuts. One common type of femoral prothesis has a J-shape. A femoral prosthesis is usually metallic, having a highly polished outer femoral articulating surface.

A common type of tibial prosthesis uses a laterally extending tray that is shaped to conform to the patient's proximal tibia after the proximal tibia has been cut transversely by the surgeon. The tibia prosthesis also includes a stem or plug that extends generally perpendicular to the tray and from the center of the tray. The stem is placed in a surgically formed opening that extends into the patient's intramedullary canal from the transverse cut formed on the proximal tibia.

A plastic, polymeric insert is attached to the tibial tray. This insert provides a tibial articulating surface that articulates with the femoral articulating surface as the patient's tibia moves through a full range of motion with respect to the patient's femur.

One of the problems with knee joint replacement surgery is that of accurately fitting the patient. Each patient has a different bone structure and geometry. Even though the surgeon uses x-rays to study a particular patient's anatomy at the knee, the surgeon does not have a perfect appreciation of the patient's anatomy until after the knee has been surgically exposed and the surgeon begins to make cuts on the femur and the tibia.

Knee prosthetic components are not available in infinite sizes. The surgeon must examine the patient's anatomy, make the requisite surgical cuts and install prosthesis components that fit.

A number of tibial components have been patented that relate to tibial components having a tray, a plastic insert with articulating surface, and a stem portion that provides initial fixation when the prosthesis is implanted. Other patents have issued that relate to cutting instrumentation for preparing the patient's proximal tibia to receive a tibial prosthetic insert as part of knee joint replacement surgery.

The Murray U.S. Pat. No. 4,016,606 discloses a knee prosthesis that includes a tibial component with a tray and with a stem adapted to be received in a longitudinal bore in the patient's femur. The stem has one end that is integral with a depending generally spheroidal surface having generally the same radius as the radius of the spheroidal depression in the insert.

In the Chiarizzio U.S. Pat. No. 4,601,289 there is disclosed a femoral trial prothesis/rasp assembly used in hip implant surgery. The assembly includes a handle that grips the combination trial prothesis/rasp in a secure manner by clamping over and locking on to a post on the trial prothesis/rasp which later serves as a mounting piece for a femoral prothesis head used in trial reductions.

A modular tibial prosthesis is disclosed in the Shaw U.S. Pat. No. 4,938,769. The Shaw patent discloses a tibial prosthesis for use during a total knee arthroplasty procedure which includes a modular two part tibial component comprising an in-bone anchorage assembly to which is removably attached a tibial tray adapted to receive and retain a bearing insert. Removal of the tray permits access to the interface between the bone and anchorage assembly in the event removal or revision are necessary. In preferred embodiments, the invention affords hybrid fixation of the tibial prosthesis in that bone cement for immediate fixation and adaptation for longer term bone ingrowth are featured. Shaw also discusses the use of porous coatings to enhance fixation.

U.S. Pat. No. 4,938,769 issued to James Shaw discloses an end bone anchorage assembly for a tibial prosthesis that includes an axially elongated central stem and a plurality of elongated fixation pegs spaced from the stem. The stem and the pegs have proximal and distal ends. The proximal ends of the stem define an attachment table. A plurality of structural links interconnect the pegs and the stem. Means is provided for removably attaching a tibial tray to the assembly wherein each of the pegs is connected to the stem by the structural link.

A tibial component for a replacement knee prosthesis is disclosed in the Lawes et al. U.S. Pat. No. 5,080,675. Lawes discloses a tibial component for a replacement knee prosthesis comprising a tibial tray for connection to a suitably prepared tibia, the tray carrying fixed lateral and medial condylar bearing components. Only the medial component has a shock absorber located beneath it.

U.S. Pat. No. 5,137,536 issued to Tomihisa Koshino describes a tibial component for an artificial knee joint. The tibial component includes a plate section having an upper surface and a pair of bearing surfaces parts that are adapted to be in sliding contact with a femoral component. A stem portion extends downwardly from a lower surface of the plate section. A pair of blade like members extend obliquely and posteriorly from the stem. The plate section has a lower surface with a plurality of elongated grooves for improving affinity with respect to the surrounding bone, the grooves including a first group of grooves and a second set of group of grooves extending perpendicularly to the first group of grooves.

An example of a modular tibial support is seen in the Elias U.S. Pat. No. 5,246,459 entitled "Modular Tibial Support Pegs for the Tibial Component of a Prosthetic Knee Replacement System". The Elias Patent discloses a modular tibial support peg operable to secure a tibial component of a knee joint prothesis to a tibia having a groove. The modular tibial support peg includes a cylindrical body with a ridged outer surface operable to engage the groove in the tibia. The modular tibial support peg further includes a plurality of spikes extending inferiorly from the cylindrical body. The spikes are operable to engage the tibia at the inferior end of the groove.

SUMMARY OF THE INVENTION

The present invention provides an improved method of preparing a patient's proximal tibia with a surgical saw. The method of the present invention uses cutting instrumentation for guiding the saw when shaping the patient's proximal tibia with cuts to receive a tibial implant.

The patient's tibial intramedullary canal is first drilled to receive an intramedullary rod. The surgeon then places the rod in the intramedullary canal and mounts cutting guide instruments to that rod as part of the method of the present invention.

A first cutting instrument is mounted on the rod above the patient's proximal tibia. The first cutting instrument has transverse cutting guide surfaces for guiding a surgical saw during an initial cutting of the proximal tibia. The first cutting instrument also provides a stylus with an adjustable stylus member that can reference the proximal tibia before cutting begins. The surgeon then sets a selected depth of cut with the stylus and engages the proximal tibial surface with the stylus.

After the depth of cut has been set using the stylus, the proximal tibia is cut with a first transverse cut. During this first cut, the saw tracks the cutting guide surfaces and then engages the proximal tibial bone tissue. The first cutting instrument and its stylus are then removed.

A second cutting instrument is then mounted on the rod above the patient's proximal tibia. The second cutting instrument has guide surfaces externally of the proximal tibia for guiding a surgical saw blade and a cutter thereon that includes multiple blades for cutting longitudinally into the proximal tibia. After the secondary cutting instrument is mounted into position, a secondary transverse cut is made on the proximal tibia using the secondary cutting instrument. The saw first tracks the guide surfaces externally of the proximal tibia and then tracks a cutting guide surface on the blades.

In the preferred method of the present invention, the primary and secondary cuts are made generally perpendicular to the rod and thus to the patient's intramedullary canal.

With the method of the present invention, the cutter on the secondary cutting instrument includes a plurality of flat blades that are thrust completely into the patient's proximal tibial bone tissue. The blades are imbedded in the proximal tibia. The top surface of the cutter blades is slightly below the surface of the first transverse cut. This allows the surgeon to use the secondary cutting instrument to track not only the secondary cutting instruments externally of the tibia but also to track a guide surface provided on the upper surface of the cutter blades that have been imbedded in the patient's proximal tibial bone tissue.

BRIEF DESCRIPTION OF THE DRAWINGS

For a further understanding of the nature and objects of the present invention, reference should be had to the following detailed description, taken in conjunction with the accompanying drawings, in which like parts are given like reference numerals, and wherein:

FIG. 1 is a perspective schematic view illustrating preliminary tibial preparation;

FIG. 2 is a schematic perspective view illustrating attachment of an ankle clamp and the preferred embodiment of the apparatus of the present invention illustrating the tibial cutting block and tibial stylus portions thereof.

FIG. 3 is a perspective view illustrating the tibial cutting block and the tibial stylus portion of the preferred embodiment of the apparatus of the present invention;

FIG. 4 is a fragmentary perspective view illustrating a cutting of the proximal tibial using the tibial cutting block;

FIG. 5 is a perspective exploded view illustrating the tibial cutting block and the tibial stylus portion of the preferred embodiment of the apparatus of the present invention;

FIG. 6 is an exploded perspective view illustrating the tibial stylus;

FIG. 6A is a sectional elevational fragmentary view illustrating the tibial stylus;

FIG. 7 is a top view illustrating the tibial stylus portion of the preferred embodiment of the apparatus of the present invention;

FIG. 8 is partial sectional view illustrating the tibial stylus;

FIG. 9 is partial perspective view of the tibial stylus;

FIG. 10 is a fragmentary view of the tibial stylus:

FIG. 11 is another fragmentary sectional view of the tibial stylus;

FIG. 12 is a fragmentary sectional view of the preferred embodiment of the apparatus of the present invention;

FIG. 13 is a front elevational view of the tibial cutting block portion of the preferred embodiment of the apparatus of the present invention;

FIG. 14 is a top view of the tibial cutting block of the preferred embodiment of the apparatus of the present invention;

FIG. 15 is a sectional view of the tibial cutting block of the preferred embodiment of the apparatus of the present invention;

FIG. 16 is a partial sectional view of the tibial cutting block of the preferred embodiment of the apparatus of the present invention;

FIG. 17 is a perspective view illustrating placement of the tibial secondary prep-guide portion of the preferred embodiment of the apparatus of the present invention;

FIG. 18 is a perspective view illustrating the tibial secondary prep-guide and a secondary finishing of the proximal tibia;

FIG. 19 illustrates installation of a trial tibial prosthesis in the patient's proximal tibia;

FIG. 20 illustrates the trial femoral prosthesis and the trial tibial prosthesis installed respectively on the patient's distal femur and proximal tibia and prior to rotation to the tibial trial prosthesis;

FIG. 21 is a perspective view of the tibial secondary prep-guide portion of the preferred embodiment of the apparatus of the present invention;

FIG. 22 is a frontal elevational view of the tibial secondary prep-guide;

FIG. 23 is an elevational side view of the tibial prep-guide;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1-4 illustrate a preliminary preparation of the patient's distal tibia as part of the method of the present invention. In FIG. 1, the patient's tibia 10 is shown as is the proximal tibia 11. A drill 13 is used to track the patient's intramedullary canal 12 for receiving a reamer 21. Also shown in FIG. 1 is the patient's femur 14 that has already been surgically prepared to receive a trial femoral prosthesis. The distal femur 15 is typically prepared with anterior and posterior cuts that are parallel to each other, a distal cut that is generally perpendicular to the anterior and posterior cuts, and diagonally extending chamfer cuts that extend between the distal cut and the respective posterior and anterior cuts.

In FIG. 2, an ankle clamp 16 has been installed at the patient's ankle 17 and with an alignment sleeve 18 that is positioned generally parallel to the patient's tibia. The sleeve 18 provides a coupling 19 for forming a connection with the bottom of tibial cutting guide 20 of the present invention. Ankle clamps 16 are commercially available and can be seen for example in the Steele U.S. Pat. No. 5,197,944, incorporated herein by reference.

In FIG. 3, the tibial cutting guide 20 can be seen placed adjacent the patient's proximal tibia 11. In FIGS. 3 and 5-6, the tibial cutting guide 20 can be seen attached to the tibial stylus 50, and the assembly of cutting guide 20 and stylus 50 being attached to reamer 21 mounted in the patient's intramedullary canal. Stylus 50 is shown more particularly in FIGS. 5-12. Cutting block 20 is shown more particularly in FIGS. 13-16.

Cutting block 20 includes a block body 22 that includes a pair of upper flanges 23 and a pair of lower flanges Slots 25, 26 extend between the upper flanges 23 and the lower flanges 24. The slots 25, 26 provide a guide for a flat cutting blade such as the cutting blade 73 shown in FIG. 4 which can be a commercially available powered saw. The saw blade 73 cuts through the patient's proximal tibia 11 as shown in FIG. 4 along a line 74 that is generally perpendicular to the patient's intramedullary canal. In FIG. 4, the block 22 has been attached to the proximal tibia 11 using a plurality of bone spikes 30.

Tibial cutting block 22 further provides a center portion 22 that can be used to attach the cutting block 22 to the tibial stylus 50 and to ankle clamp 16 at coupling 19. Cutting block body 22 provides a lower attachment portion 28 having a plurality of cylindrical bores 29 therethrough as shown in FIGS. 13 and 14. These cylindrical openings 29 provide a cylindrical shape that corresponds generally to the outer configuration of a bone spike 30. One or more bone spikes can be placed through a corresponding plurality of the openings 29 for affixing the block 22 to the patient's proximal tibia after alignment has been accomplished using elongated reamer rod 21 placed in the patient's intramedullary canal, the stylus 50, and ankle clamp 16.

Vertical rod 31 extends from coupling 19 to center portion 27 of tibial cutting block 22. A set screw 32 threadably engages opening 33 of central portion 28 of cutting block 22. Cylindrical socket 34 receives the upper end of vertical rod 31. The set screw 32 can be tightened against the rod as it occupies the cylindrical socket 34.

An upper cylindrically-shaped internally threaded opening 35 allows the cutting block 22 to be attached to tibial stylus 50. Vertical post 36 extends between stylus 50 and cutting block 22. The post 36 has a central longitudinal axis that is perpendicular to the plane defined by slots 25, 26. Further, the central longitudinal axis of post 36 is parallel to the central longitudinal axis of reamer rod 21 that is mounted in the patient's intramedullary canal. The post 36 has a lower end 37 with a pair of flanges 38, 39 having a recess 40 therebetween.

An upwardly projecting portion 41 of the center portion 28 of cutting block 22 registers in the recess 40. Further, the flanges 38, 39 closely conform to the projecting portion 41 upon assembly. A threaded connection can be used to form a connection between the threaded opening 35 and bolt 49 that extends through vertical bore 46 of vertical post 36. A bolted connection can be used to assemble the vertical post 36 to the cutting block 22, for example.

A pair of shoulders 44, 45 at the upper end of vertical post 36 register in an elongated slot 53 on tibial stylus 50. The upper end 43 of post 36 has a transverse cross section that corresponds in size and shape to the transverse cross section of the longitudinally extending slot 53. Slot 53 extends through horizontal beam 51 or tibial stylus 50. The slot 53 communicates with a longitudinal opening 52 in the upper surface of the horizontal beam 51. A transverse probe holder 54 extends at generally right angles to the beam 51. A bushing 55 extends upwardly from the connection between beam 51 and probe holder 54. The bushing 55 provides a vertical open ended bore 56 that receives reamer 21. Set screw 57 can be used to tighten bushing 55 and the entire tibial stylus 50 to reamer 21. Internally threaded opening 70 receives the set screw 57.

Probe holder 54 includes a pair of sides 58, 59 each having an elongated vertically extending probes 60, 61 respectively. The probe holder 54 has an upper generally flat surface 62 that is perpendicular to the central longitudinal axis of bore 56 and to the central longitudinal axis reamer rod 21. Each probe 60, 61 moves vertically in an opening 66, 67 respectively. A pair of horizontal openings 68, 69 carry detent locking members 63, 64 respectively. The detent locking members 63, 64 can be spring loaded with sprpings 97, 98. Each of the detent locking members 63, 64 have openings that allow the probes 60, 61 to pass therethrough. Each probe 60, 61 provides a plurality of vertically spaced teeth 76 thereon (see FIG. 6). Spaces between the teeth 76 are engaged by the respective detent locking member 63, 64 at stop 96 when they are released, thereby affixing the position of each of the probes 60, 61 relative to the probe holder 54. A stop pin 101 holds each detent locking member 63, 64 in its opening 68, 69.

Longitudinal opening 52 is surrounded by side walls 72 and by longitudinally extending shoulders 71. This allows the placement of a bolt 49 into slot 52 and through the center of vertical bore 46 of vertical post 36 for attaching to threaded opening 35. Further, the head 43 of the bolt 49 rests on the shoulder 71 transferring load thereto.

In FIGS. 17-18 and 21-23, there can be seen tibial secondary prep guide 75. Guide 75 has an instrument body 76 that includes a pair of spaced apart vertical posts including the post 77 and the post 82. Post 77 carries a cylindrical cutting element 78 with a plurality of circumferentially spaced and radially extending cutting blades 79-81. The post 82 supports a pair of flanged portions including upper flanges 83 and lower flanges 84.

A pair of flat cutting blade guide slots 85, 86 are positioned between the upper flanges and the lower flanges 84, as shown in FIGS. 21-23. During use, the surgeon places the tibial secondary prep guide over the reamer 21 that is installed in the patient's intramedullary canal. This registers the three cutting blades 79-81 and the cylindrical cutting element 78 at the center of the patient's proximal tibia 11, as shown in FIG. 17.

The surgeon hammers the flat side 88 of instrument body 76 driving the cutting blades 79-81 into the proximal tibia 11 as shown in FIGS. 17-18. The surgeon hammers the surface 88 until the blades 79-81 are just beneath the surface of proximal tibia 11 as shown in FIG. 18. This allows the surgeon to shave a layer of tissue from proximal tibia 11 with great precision. The saw blade 89 is supported not only by the flanges 83, 84, but also by the upper surfaces 90 of blades 79-81 which are in a common plane with the upper surface 91 of the flange 84, as shown in FIG. 31. The dotted line 102 in FIG. 21 shows the path taken by saw blade 89 to secondarily cut the proximal tibia.

After the secondary cut is made to the proximal tibia 11, a trial prosthesis can be installed on the patient's distal tibia 11. In FIGS. 19-20, a tibial trial prosthesis 92 is shown as installed into the patient's intramedullary canal 12. The tibial trial prosthesis 92 can include three components, a metallic plate or tray 93, a stem or plug 94, and a plastic trial insert 95. In FIG. 20, a tibial prosthesis 92 has been installed by the surgeon on the patient's proximal tibial 11. The surgeon has also installed a trial femoral prosthesis 100 on the distal femur 15.

The following table lists the parts numbers and parts descriptions as used herein and in the drawings attached hereto.

    ______________________________________                                         PARTS LIST                                                                     Part Number     Description                                                    ______________________________________                                         10              tibia                                                          11              proximal tibia                                                 12              intramedullary canal                                           13              drill                                                          14              femur                                                          15              distal femur                                                   16              ankle clamp                                                    17              ankle                                                          18              alignment sleeve                                               19              coupling                                                       20              tibial cutting guide                                           21              elongated reamer rod                                           22              cutting block body                                             23              upper flange                                                   24              lower flange                                                   25              horizontal slot                                                26              horizontal slot                                                27              center portion                                                 28              attachment portion                                             29              cylindrical bores                                              30              bone spikes                                                    31              vertical rod                                                   32              set screw                                                      33              internally threaded opening                                    34              cylindrical socket                                             35              internally threaded opening                                    36              vertical post                                                  37              lower end                                                      38              flange                                                         39              flange                                                         40              recess                                                         41              projecting portion                                             43              head                                                           44              shoulder                                                       45              shoulder                                                       46              vertical bore                                                  47              recess                                                         48              recess                                                         49              bolt                                                           50              tibia1 stylus                                                  51              horizontal beam                                                52              longitudinal opening                                           53              longitudinal opening                                           54              probe holder                                                   55              bushing                                                        56              vertical open ended bore                                       57              set screw                                                      58              side                                                           59              side                                                           60              probe                                                          61              probe                                                          62              flat surface                                                   63              detent locking member                                          64              detent locking member                                          65              bolted connection                                              66              opening                                                        67              opening                                                        68              horizontal opening                                             69              horizontal opening                                             70              internally threaded opening                                    71              longitudinally extending                                                       shoulder                                                       72              side wall                                                      73              saw blade                                                      74              transverse cut                                                 75              tibial secondary prep guide                                    76              body                                                           77              vertical post                                                  78              cylindrical cutting element                                    79              blade                                                          80              blade                                                          81              blade                                                          82              vertical post                                                  83              upper horizontal flange                                        84              lower horizontal flange                                        85              cutting guide slot                                             86              cutting guide slot                                             87              open ended vertical bore                                       88              flat surface                                                   89              blade                                                          90              upper surface                                                  91              upper surface                                                  92              trial prosthesis                                               93              tray                                                           94              stem                                                           95              insert                                                         96              stop                                                           97              spring                                                         98              spring                                                         99              opening                                                        100             opening                                                        101             stop pin                                                       102             transverse cutting plane                                       ______________________________________                                    

Because many varying and different embodiments may be made within the scope of the inventive concept herein taught, and because many modifications may be made in the embodiments herein detailed in accordance with the descriptive requirement of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense. 

What is claimed as invention is:
 1. A tibial stylus apparatus comprising:a) an instrument body; b) a reference member that can track the patient's intramedullary canal so that the reference member enables the surgeon to reference surgical cuts with respect to the patient's intramedullary canal; c) the body having cutting guide surfaces for guiding a surgeon's cutting blade during a cutting of the patient's proximal tibia; d) adjustable stylus carried by the instrument body for setting a depth of cut at either of the patient's medial and lateral condylar surfaces; and e) the stylus including a pair of adjustable stylus probe members each independently adjustable relative to the instrument body.
 2. The tibial stylus apparatus of claim 1 further comprising means for adjusting the instrument body position at the cutting guide surfaces relative to the referencing member in the anterior-posterior direction.
 3. The tibial stylus apparatus of claim 1 wherein the instrument body comprises a plurality of separate, interconnectable body members including a first body member having transverse cutting guides surfaces thereon for guiding a surgeon's cutting blade during a transverse cutting of the proximal tibia, a second body member carrying the stylus means and a third body member forming a connection between the first body member and the second body member.
 4. The tibial stylus apparatus of claim 1 wherein the rod forms a connection with the instrument body and wherein the cutting guide surfaces define a plane that transversely intersects the rod.
 5. A tibial stylus apparatus comprising:a) an instrument body having mounting means for attaching the instrument body to a patient's proximal tibia; b) said mounting means including a rod that can track the patient's intramedullary canal so that the rod enables the surgeon to reference surgical cuts with respect to the patient's intramedullary canal; c) the body having cutting guide surfaces for guiding a surgeon's cutting blade during a cutting of the patient's proximal tibia; d) adjustable stylus means carried by the instrument body for setting a depth of cut at either of the patient's medial and lateral condylar surfaces; and e) wherein the instrument body comprises a block member attachable to the patient's proximal tibia, a vertical strut having a lower end portion and an upper end portion, a horizontal strut that carries said stylus means, means for forming a connection between the lower end portion of the vertical strut and the block member, and means for forming a connection between the upper end portion of the vertical strut and the horizontal strut.
 6. The tibial stylus apparatus of claim 5 wherein the horizontal strut comprises a horizontal member having a pair of arms, each arm carrying a stylus probe member, each stylus probe member being adjustably connectable along its length relative to the patient's proximal tibia so that either stylus probe member can be used by the surgeon to set a depth of cut.
 7. A tibial stylus apparatus comprising:a) an instrument body having mounting means for attaching the instrument body to a patient's proximal tibia; b) said mounting means including a rod that can track the patient's intramedullary canal so that the rod enables the surgeon to reference surgical cuts with respect to the patient 's intramedullary canal; c) the body having cutting guide surfaces for guiding a surgeon's cutting blade during a cutting of the patient's proximal tibia; d) adjustable stylus means carried by the instrument body for setting a depth of cut at either of the patient's medial and lateral condylar surfaces; and e) wherein the stylus means comprises a pair of probes that are adjustably mounted to the instrument body.
 8. The tibial stylus apparatus of claim 7 wherein the probes are generally parallel.
 9. The tibial stylus apparatus of claim 8 wherein each of the probes is independently adjustable relative to the instrument body.
 10. The tibial stylus apparatus of claim 9 each of the probes is affixable into a known position relative to the instrument body and further comprising indicia means for indicating the distance between each probe and the cutting guide surfaces.
 11. A tibial stylus apparatus comprising:a) an instrument body having mounting means for attaching the instrument body to a patient's proximal tibia; b) a rod that can track the patient's intramedullary canal so that the rod enables the surgeon to reference surgical cuts with respect to the patient's intramedullary canal; c) the body having cutting guide surfaces for guiding a surgeon's cutting blade during a cutting of the patient's proximal tibia; and d) stylus means for setting a depth of cut at a selected condylar surface area of the patient's medial or lateral condylar surfaces, said stylus means including a pair of adjustable stylus probe members each independently adjustable relative to the instrument body.
 12. The tibial stylus apparatus of claim 11 wherein the pair of stylus probes are generally parallel.
 13. A tibial stylus apparatus comprising:a) an intramedullary rod that can fit a patient's tibial intramedullary canal, tracking the intramedullary canal axis; b) instrument body having an opening that registers with the intramedullary rod so that the body can be affixed to the rod at the opening, said body having means for enabling the surgeon to adjust the instrument body along an anterior to posterior path; c) a pair of stylus probes mounted on the instrument body, each of said probes being adjustable relative to the body and to one another to define a selective depth of cut; d) the body including a cutting guide having cutting guide surfaces thereon that enable the surgeon to transversely cut the patient's proximal tibia by tracking the cutting guide surfaces with a cutting blade, said cutting guide surfaces being affixed to said instrument body so that adjustment of a selected probe relative to the instrument body also adjusts the distance between a selected probe and the cutting guide surfaces.
 14. The tibial stylus apparatus of claim 13 wherein each stylus probe has a toothed rack thereon, and the instrument body carries means for engaging a selected tooth of the toothed rack.
 15. The tibial stylus apparatus of claim 13 wherein each stylus probe is generally parallel to the rod.
 16. The tibial stylus apparatus of claim 13 wherein the pair of probes are parallel.
 17. The tibial stylus of claim 13 further comprising means for setting the position of a selected probe so that the surgeon likewise sets the depth of cut.
 18. The tibial stylus of claim 13 wherein a pair of probes are independently adjustable so that the surgeon can measure a depth of cut at either the medial or lateral knee area.
 19. The tibial stylus of claim 13 wherein one probe measures depths of cut at the medial side of the knee and the other probe measures depth of cut at the lateral side of the patient's knee.
 20. The tibial stylus apparatus of claim 13 wherein a selected probe is positioned to touch a lateral or a medial side of the patient's knee for setting a depth of cut.
 21. The tibial stylus apparatus of claim 13 wherein the cutting block has a portion that adjusts relative to the rod along an anterior to posterior path so that the surgeon can position the cutting guide surfaces very close to the patient's tibia.
 22. The tibial stylus apparatus of claim 13 further comprising means for locking a stylus probe to the instrument body at a selected position along the length of the probe.
 23. A tibial stylus apparatus comprising:a) an instrument body having mounting means for attaching the instrument body to a patient's proximal tibia; b) said mounting means including a referencing member that enables the surgeon to reference surgical cuts with respect to the patient's tibia; c) the body having cutting guide surfaces for guiding a surgeon's cutting blade during a cutting of the patient's proximal tibia; d) adjustable stylus means carried by the instrument body for setting a depth of cut at either of the patient's medial and lateral condylar surfaces; and e) wherein the stylus means comprises a pair of probes that are adjustably mounted to the instrument body.
 24. The tibial stylus apparatus of claim 23 further comprising means for adjusting the instrument body position at the cutting guide surfaces relative to the rod in the anterior-posterior direction.
 25. The tibial stylus apparatus of claim 23 wherein the instrument body comprises a block member attachable to the patient's proximal tibia, a vertical strut having a lower end portion and an upper end portion, a horizontal strut that carries said stylus means, means for forming a connection between the lower end portion of the vertical strut and the block member, and means for forming a connection between the upper end portion of the vertical strut and the horizontal strut.
 26. The tibial stylus apparatus of claim 25 wherein the horizontal strut comprises a horizontal member having a pair of arms, each arm carrying a stylus probe, each stylus probe being adjustably connectable along its length relative to the patient's proximal tibia so that either stylus probe can be used by the surgeon to set a depth of cut.
 27. The tibial stylus apparatus of claim 23 wherein the instrument body comprises a plurality of separate, interconnectable body members including a first body member having transverse cutting guides services thereon for guiding a surgeon's cutting blade during a transverse cutting of the proximal tibia, a second body member carrying the stylus means and a third body member forming a connection between the first body member and the second body member.
 28. The tibial stylus apparatus of claim 23 wherein the referencing member is an elongated rod.
 29. The tibial stylus apparatus of claim 28 wherein the rod forms a connection with the instrument body and wherein the cutting guide surfaces define a plane that transversely intersects the rod.
 30. The tibial stylus apparatus of claim 23 wherein the probes are generally parallel.
 31. The tibial stylus apparatus of claim 30 wherein each of the probes is independently adjustable relative to the instrument body.
 32. The tibial stylus apparatus of claim 23 each of the probes is affixable into a known position relative to the instrument body and further comprising indicia means for indicating the distance between each probe and the cutting guide surfaces.
 33. The tibial stylus apparatus of claim 23 wherein each stylus probe has a toothed rack thereon, and the instrument body carries means for engaging a selected tooth of the toothed rack.
 34. The tibial stylus apparatus of claim 28 wherein each stylus probe is generally parallel to the rod.
 35. The tibial stylus of claim 23 further comprising means for setting the position of a selected probe so that the surgeon likewise sets the depth of cut.
 36. The tibial stylus of claim 23 wherein one probe measures depths of cut at the medial side of the knee and the other probe measures depth of cut at the lateral side of the patient's knee.
 37. The tibial stylus apparatus of claim 28 wherein the cutting block has a portion that adjusts relative to the rod along an anterior to posterior path so that the surgeon can position the cutting guide surfaces very close to the patient's tibia.
 38. The tibial stylus apparatus of claim 23 further comprising means for locking a stylus probe to the instrument body at a selected position along the length of the probe. 